FR2945098A1 - DEVICE FOR PROTECTING AT LEAST ONE CONDUIT LOCATED AT THE BOTTOM OF A WATER EXTEND AND ASSOCIATED FLUID TRANSPORT ASSEMBLY - Google Patents

Abstract

This device comprises a plurality of disjoint elements (24) for ballasting the pipe. Each ballast element (24) has a bottom surface (34) to be placed on the bottom (12) of the body of water (14) and an upper surface (32) defining at least one concave channel (38). conducting support (16A, 16B). The device (18) further includes a conduit top cover (26) connecting at least two disassembled ballast elements (24) to cover the conduit (16A, 16B) between the ballast elements (24). The cap (26) extends opposite the gutter (38) and delimits with the upper surface (32) of each ballast element (24) a passage for receiving the pipe (16A, 16B).

Description

The present invention relates to a device for protecting at least one pipe disposed at the bottom of an expanse of water. , of the type comprising a plurality of disassembled ballast elements of the pipe, each ballast element having a lower surface to be placed on the bottom of the body of water and an upper surface delimiting at least one support gutter. the driving. Such a device is particularly applicable to the protection of fluid transport pipes resting on the bottom of a body of water, such as a sea, an ocean, or a lake.

The pipe is intended in particular to carry a fluid, such as for example hydrocarbons, gases or mixtures of gases and fluids, between a wellhead located on the bottom of the body of water and a convergence zone where join several conduits. The fluids collected in the convergence zone go back to a surface installation via one or more risers. Offshore hydrocarbon production fields are known which include a multitude of wellheads and thus a large number of transport pipes extending on the seabed. It is therefore sometimes necessary to immobilize these pipes relative to each other on the seabed, to prevent them from moving under the effect of underwater currents and prevent them from damaging the neighboring pipes or still underwater equipment. For this purpose, it is known to provide the conduct of passive ballast elements that stabilize the position of the pipe on the seabed, thanks to the melting weight of the ballast elements. These ballasting elements consist for example of a concrete coating surrounding the pipe along its entire length or concrete ring elements distributed at intervals along the pipe as described for example in the French application FR-A-2,400. 657.

Such a device, however, has a very high mass which complicates the handling and installation of the pipe at the bottom of the body of water.

In addition, such a device provides only partial protection of the pipe, particularly against the impacts caused by falling objects or underwater interventions. This protection may be necessary, however, particularly in the context of the transport of cryogenic liquids such as liquefied natural gas (LNG) which are maintained at a temperature in the region of -160 ° C. In this case, the pipes used have a double insulating jacket whose integrity must be protected to ensure the safe transport of the fluid.

An object of the invention is therefore to provide a device for protecting a pipe disposed in the bottom of a body of water, which is simple to install and low mass, while providing good protection of the pipe. To this end, the subject of the invention is a device of the aforementioned type, characterized in that the device further comprises an upper protective pipe cap connecting at least two disassembled ballast elements to cover the pipe between the ballast elements, the cap extending opposite the gutter and delimiting with the upper surface of each ballast element a passage for receiving the pipe. The device according to the invention may comprise one or more of the following characteristics, taken alone or in any combination (s) technically possible (s): - at least two ballasting elements carry fastening means the cap on the ballast elements; - The cap has substantially a cylinder shape of concavity cylinder directed downwards; the cap has a lower surface of minimum radius of curvature greater than the maximum radius of curvature of the upper surface of the ballasting element opposite in the gutter; - the cap defines, between two adjacent ballast elements, at least one volume released downward in the absence of driving; the lower surface of at least one ballast element has a curved portion of convexity directed downwards; - The domed portion has a central region substantially parallel to an axis of immobilization of the pipe in the ballast element and at least one peripheral region inclined to the upper surface away from the central region; - At least one ballasting element is made based on a first material, preferably concrete, the cap being made based on a second material, preferably a plastic material, a metallic material or a composite material; the upper surface of each ballast element delimits at least two gutters each intended to support a separate pipe, the device comprising, opposite each gutter, an upper pipe protection cap connecting at least two disassembled ballast elements to cover the driving between the ballast elements, the cap extending opposite the gutter; and the cap has a plurality of end-to-end cap members, each cap member having an upstream end carried by a first ballast member, and a downstream end supported by a second ballast member adjacent to the first ballast member. . The invention also relates to a fluid transport assembly on the bottom of a body of water characterized in that it comprises: at least one rigid pipe for transporting fluid; and - a protection device as defined above, the pipe being disposed in the receiving passage between the cap and each ballast element, resting on each ballast element. The transport assembly according to the invention may comprise one or more of the following characteristics, taken singly or in any combination (s) technically possible: - the pipe is applied to the surface upper being inserted into each channel, the cap being disposed away from the pipe; and the cap angularly covers the pipe upwards over an angular sector of angle greater than 90 °, advantageously with an angle substantially equal to 180 ° around the axis of the pipe.

The invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended drawings, in which: FIG. 1 is a partial perspective view of three-quarters face of a first transport assembly according to the invention comprising a protective device disposed on the bottom of a body of water; Figure 2 is a bottom view of the device of Figure 1; - Figure 3 is a view taken in section along the vertical plane III of Figure 1; and - Figure 4 is a bottom view of a detail of the protective device of Figure 1. In all that follows, the terms upstream and downstream generally agree with respect to the normal direction of flow of a fluid. Figures 1 to 4 illustrate a first fluid transport assembly 10 according to the invention resting on the bottom 12 of a body of water 14. This assembly 10 is totally immersed under the surface of the body of water 14. The body of water 14 is for example a lake, a sea, or an ocean. It has a depth of water, taken between the bottom and the surface to the right of the assembly 10, for example greater than 15 m and in particular between 30 m and 3500 m. The transport assembly 10 is intended to convey a fluid, in particular hydrocarbons, between a production unit (not shown) situated on the bottom 12 of the water body 14 upstream of the transport assembly 10, and a convergence zone (not shown), located downstream of the transport assembly 10, from which the fluid is transported to the surface of the body of water 14. The transport assembly 10 comprises at least one less a fluid transport conduit 16A, 16B, and a protection device 18 of the or each pipe 16A, 16B according to the invention.

In the example shown in Figure 1, the transport assembly 10 comprises two parallel transport pipes 16A, 16B, the pipe 16B having a diameter smaller than that of the pipe 16A.

More generally, the transport assembly 10 may comprise a single pipe 16A, or a number of pipes greater than two. Each conveying conduit 16A, 16B internally defines a fluid flow passage 20. This passage 20 is connected upstream to the production assembly and downstream to a riser for the continuous transport of the fluid between the production assembly and a surface recovery plant. The pipe 16A, 16B may be based on an assembly of simple metal tubes or based on an assembly of metal tubes covered with a layer of thermal insulation itself optionally covered with a sheath of polymeric material. In this example, the pipe 16A, 16B is a rigid pipe made for example based on a metal tube or an assembly of metal tubes. Each conduit 16A, 16B extends longitudinally along an axis A-A 'which is horizontal in the Figures.

In the example shown in Figures 1 to 4, each pipe 16A, 16B is formed of a single tubular wall internally defining a fluid circulation passage 20. Alternatively (not shown), the pipe 16A, 16B comprises a double cylindrical envelope delimiting an annular space filled with an insulating material. In a variant, the pipe 16A, 16B comprises a cylindrical double jacket intended for the transport of a cryogenic fluid such as liquefied natural gas (LNG). The protection device 18 comprises a plurality of elements 24 for ballasting and supporting each pipe 16A, 16B, and for each pipe 16A, 16B, a separate protective longitudinal cap 26 attached to the ballast elements 24 via Fastening means 28. The ballasting elements 24 are distributed longitudinally along the length of each pipe 16A, 16B. They are spaced longitudinally from each other by a distance of a few meters, preferably about ten meters. In this example, each ballast element 24 carries two parallel lines 16A, 16B. Each element 24 is formed of a heavy body 30 made of a first material which is advantageously concrete.

The body 30 defines an upper surface 32 of pipe support, a lower surface 34 placed against the bottom 12 of the body of water 14, and a lateral surface 36 connecting the surfaces 32, 34. The body 30 has a width, taken perpendicular to the axis A-A ', greater than the total width of the conduits 16A, 16B. It has a length, taken parallel to the axis A-A ', less than the length of the gap separating two consecutive ballasting elements 24. The upper surface 32 extends generally horizontally when the lower surface 34 is placed on a horizontal bottom 12.

As illustrated in FIG. 3, the upper surface 32 delimits, for each pipe 16A, 16B, a concave trough 38 for receiving the pipe 16A, 16B, and on either side transversely of each trough 38, flat regions 40 28. Each gutter 38 opens longitudinally upstream and downstream of the body 30. Each channel 38 has a concavity directed upwards. In this example, each channel 38 has a cross section, taken in a plane perpendicular to the axis A-A ', substantially in the form of a circular arc, of radius conjugated to the outer radius of the pipe 16A, 16B that it receives.

The channel 38 extends over an angular sector around the axis A-A ', with an angle greater than 60 °, in particular with an angle substantially equal to 90 ° around this axis A-A'. Thus, when the pipe 16A, 16B is disposed in the channel 38, its periphery is in contact with the upper surface 32 in the trough 38 along at least two generatrices of the pipe, taken along the axis A-A '. This prevents inadvertent transverse displacement of the pipe 16A, 16B. In the example shown in Figure 3, the pipe 16A, 16B is applied against the upper surface in the channel 38 over substantially the entire angular extent of the channel 38 around the axis A-A '. The pipe 16A, 16B protrudes above the body 30 from the upper surface 32 at least over half of its diameter. It is kept completely away from the bottom 12 of the body of water 14 by the ballasting elements 24. The bottom surface 34 has a shape adapted to the characteristics of the bottom soil 12, as well as to the nature of the conduit 16A, 16B.

The lower surface 34 comprises, facing each channel 38, a domed portion 42 convexity directed downwards, and between the curved portions 42, a substantially flat intermediate connecting portion 44. Each convex portion 42 protrudes downwardly on either side transversely of the intermediate portion 44.

The curved portions 42 thus delimit between them a central channel of concavity directed downwardly opening longitudinally on either side of the body 30. Each curved portion 42 has a central region 46 substantially flat, intended to be inserted into the bottom 12 of the expanse of water 14, and an inclined peripheral region 48 converging towards the upper surface 32 from the central region 46. The central region 46 extends substantially in a plane parallel to the axis A-A ', in parallel to the flat region 40 of the upper surface 32. The distance vertically separating the axis AA 'from the plane of the central region 46 is greater than the distance separating the axis AA' from the flat region 40. In addition, the thickness and the body 30, taken between the lowest point of the channel 38 and the central region 46 is greater than the thickness e2 of the body, taken between the flat region 40 of the upper surface 32 and the intermediate portion 44. The peripheral region 48 extends around the periphery of the planar region 46. The peripheral region 48 converges towards the upper surface 32 by moving upwards from the central region 46, on the one hand laterally and longitudinally to the lateral surface 34, and secondly, laterally to the intermediate portion 44. In projection in a vertical plane, the angle of inclination B formed between the plane of the central region 46, and the peripheral region 48 is greater at 10 °, and is in particular between 10 ° and 80 ° The presence of the peripheral region 48 inclined around the flat central region 46 facilitates the movement of the transport assembly 10 on the bottom 12 of the body of water 14, especially when the pipe 16A, 16B is towed, by limiting the tensile strength generated by the protective device 18. The fastening means 28 comprise, for each ballast element 24 and for each nduite 16A, 16B, a pair of jumpers 60A, 60B facing disposed transversely on either side of the channel 38. The jumpers 60A, 60B are advantageously made of metal. The distance that separates the jumpers 60A, 60B transversely is greater than the diameter of the pipe 16A, 16B. A first rider 60A is attached to the flat region 40 of the upper surface located along a lateral edge of the body 30. A second rider 60B is attached to the flat region 40 located opposite the connecting portion 44. The riders 60A, 60B protrude upwardly from the upper surface 32. In this example, the cap 26 associated with each pipe 16A, 16B extends opposite the trough 38 receiving the pipe 16A, 16B. The cap 26 defines, with the channel 38 delimited by the upper surface 32, a receiving passage of the pipe 16A, 16B. The cap 26 extends away from the pipe 16A, 16B, delimiting above the pipe 16A, 16B, an intermediate space 60. Advantageously, an elastic material such as for example rubber is disposed in the intermediate space 60. The cap 26 thus covers the pipe 16A, 16B on an angular sector of angle y, taken about the axis A-A ', greater than 90 ° and in particular substantially equal to 180 °. It thus substantially covers the region of the pipe 16A, 16B located above a horizontal plane passing through the axis A-A 'when the element 24 is placed on a horizontal bottom 12. In this example, the cap 26 has a wall of substantially constant thickness in the form of a cut cylinder section in a plane parallel to the axis of the cylinder generated by the section.

The cap 26 has a concave inner surface 62 of concavity directed downwards. Its substantially constant thickness is less than the thickness e of the body 30 opposite the gutter 38.

Thus, in projection in a plane perpendicular to the axis A-A ', the lower surface 62 has a minimum radius of curvature centered on the axis A-A', greater than the maximum radius of curvature of the pipe 16A, 16B qu it covers and exceeds the maximum radius of curvature of the trough 38.

The cap 26 extends longitudinally parallel to the axis AA 'over a length greater than the distance longitudinally separating two ballasting elements 24 and over a length greater than the length of each ballast element 24. It advantageously extends continuously over the entire length of pipe 16A, 16B placed next to the successive ballasting elements 24, from a ballasting element 24 located furthest upstream to a ballast element 24 situated furthest downstream. It extends completely above the upper surface 32 of the ballast elements 24 and above and away from the bottom 12 of the body of water 14.

In this example, the cap 26 is made of a plurality of disjoint cap members 64, mounted end-to-end between the successive ballast elements 24. Each cap member 64 thus extends continuously between an upstream end 66 fixed on the fastening means 28 of a first ballasting element 24 and a downstream end 68 fixed on the fastening means 28 of a second adjacent ballast element 24. The attachment of the cap 26 to the fastening means 28 is for example made by screwing, riveting or bolting. Each intermediate ballasting element 24 located between two ballasting elements 24 thus carries two adjacent cap elements 64 which are fixed on the ballast element 24 by means of the fastening means 28. Each cap element 64 is thus suspended by its ends between two adjacent ballast elements 24. Between each pair of adjacent ballasting elements 24, the volume defined below the lower surface 62 in the absence of conduit 16A, 16B is not closed by a surface secured to a ballast element 24 and is released until Background 12. The protective cap 26 thus formed is particularly effective for protecting the pipe 16A, 16B against falling objects or against the impacts caused by underwater interventions. When the protective cap 26 advantageously comprises a layer of elastic material in the intermediate space 60, this also makes it possible to effectively absorb high impact energies. In addition, since the protective cap 26 is not mechanically connected to the rigid pipe 16A, 16B, the appearance of a surface defect such as a cut on the wall of the pipe 16A, 16B is considerably reduced. This is a major advantage compared to the protective device of the prior art such as concrete coatings for example. For this purpose, the cap 26 is advantageously made of a composite material such as a carbon fiber resin, made of metallic material such as steel or plastic material such as GRP (Glass Fiber Reinforced Polyester or polyester reinforced with carbon fibers). It is therefore relatively light while being mechanically resistant. The method of mounting and installing the transport assembly 10 on the bottom 12 of the water body 14 will now be described. Initially, each pipe 16A, 16B, possibly formed of different tube elements, is assembled. Ballasting elements 24 are disposed under each line 16A, 16B, distributed along line 16A, 16B. For this purpose, each pipe 16A, 16B is introduced into a channel 38 of each ballast element 24 by placing its periphery in contact with the upper surface 32 in the channel 38. The pipe 16A, 16B is thus disposed between the jumpers 60A, 60B and protrudes above the jumpers 60A, 60B.

Then, the successive cap members 64 are assembled end to end by fixing the upstream end 66 of each cap member 64 on the jumpers 60A, 60B of a first ballast element 30 and the downstream end 68 of the element. cap 64 on the riders 60A, 60B of an adjacent ballast element. A continuous protective cap 26 is thus made between the ballast elements 24 along the entire length of the pipe 16A, 16B to be protected. The transport assembly 10 thus formed is towed near the bottom of the body of water (bottom tow), then is placed on the bottom 12 of the body of water 14. The mass of each ballast element 24 , added to the mass of the pipe 16A, 16B engenders a depression in the bottom 12 of the body of water 14, which ensures good stabilization of the pipe. Once placed on the bottom 12, it is still possible to adjust the position of the pipe 16A, 16B, thanks to the advantageous shape of the lower surface 34 of the ballasting elements 24 and in particular of its inclined lateral regions 48. The transport assembly 10 according to the invention is therefore particularly simple to assemble and allows easy installation of at least one line 16A, 16B on the bottom 12 of the body of water 14, while providing adequate protection of the pipe 16A, 16B.

In addition, the protective cap 26 consisting of modules assembled end-to-end greatly facilitates inspection operations and maintenance of the pipe. In particular, it is very easy to replace one of the constituent elements of the protective cap 26 if it is damaged.

Claims (1)

1. A device (18) for protecting at least one rigid pipe (16A, 16B) disposed at the bottom of a body of water (14), of the type comprising a plurality of disjoint elements (24) for ballasting water. the pipe, each ballast element (24) having a bottom surface (34) to be placed on the bottom (12) of the body of water (14) and an upper surface (32) defining at least one gutter ( 38) for supporting the pipe (16A, 16B), characterized in that the device (18) further comprises an upper pipe protection cap (26) connecting at least two disassembled ballast elements (24) to cover the pipe (16A, 16B) between the ballast elements (24), the cap (26) extending opposite the gutter (38) and defining with the upper surface (32) of each ballast element (24) a passage of receiving the pipe (16A, 16B). 2.- Device (18) according to claim 1, characterized in that at least two ballasting elements (24) carry means (28) for fixing the cap (26) on the ballast elements (24). 3.- Device (18) according to any one of the preceding claims, characterized in that the cap (26) has substantially a cylinder shape of concavity cylinder directed downwards. 4.- Device (18) according to claim 3, characterized in that the cap has a lower surface (62) of minimum radius of curvature greater than the maximum radius of curvature of the upper surface (32) of the ballast element ( 24) facing the gutter (28). 5.- Device (18) according to any one of the preceding claims, characterized in that the cap (26) delimits, between two adjacent ballast elements (24), at least one volume discharged downwards in the absence of pipe (16A, 16B). 6.- Device (18) according to any one of the preceding claims, characterized in that the lower surface (34) of at least one ballast element (24) has a convexity curved portion (42) directed downwards. . 7.- Device (18) according to claim 6, characterized in that the curved portion (42) has a central region (46) substantially parallel to an axis (A-A ') for immobilizing the pipe (16A, 16B ) in the ballast element (24) and at least one peripheral region (48) inclined towards the upper surface (32) away from the central region (46). 8.- Device (18) according to any one of the preceding claims, characterized in that at least one ballasting element (24) is made based on a first material, preferably concrete, the cap (26) being made from a second material, preferably a plastic material, a metallic material or a composite material. 9.- Device (18) according to any one of the preceding claims, characterized in that the upper surface (32) of each ballast element (24) defines at least two gutters (38) for each to support a pipe (16A , 16B), the device (18) comprising, opposite each gutter (38), an upper pipe protection cap (26) connecting at least two disjoint ballast elements (24) to cover the pipe (16A, 16B ) between the ballast elements (24), the cap extending opposite the gutter (38). 10.- Device (18) according to any one of the preceding claims, characterized in that the cap (26) has a plurality of elements (64) of cap arranged end to end, each cap member (64) having a an upstream end (66) carried by a first ballast element (24), and a downstream end (68) carried by a second ballast element (24) adjacent to the first ballast element (24). 11.- Set (10) fluid transport on the bottom (12) of a body of water (14) characterized in that it comprises: - at least one rigid pipe (16A, 16B) fluid transport ; - A protection device (18) according to any one of the preceding claims, the pipe (16A, 16B) being arranged in the receiving passage between the cap (26) and each ballast element (24), resting on each ballast element (24). 12.- assembly (10) according to claim 11, characterized in that the pipe (16A, 16B) is applied to the upper surface (32) being inserted into each channel (38), the cap (26) being arranged to the distance from the pipe (16A, 16B). 13.- assembly (10) according to claim 12, characterized in that a layer of elastic material is interposed in the intermediate space (60) between the pipe (16A, 16B) and the cap (26). 14.- assembly (10) according to any one of claims 11 to 13, characterized in that the cap (26) angularly covers the pipe (16A, 16B) upwardly on an angular sector of greater than 90 ° angle , advantageously with an angle substantially equal to 180 ° about the axis (A-A ') of the pipe (16A, 16B).